Police have been told they are not allowed to wear a Union flag badge on their uniforms in tribute to colleagues killed on duty because it breaches regulations, it is reported.

Officers in the Metropolitan Police were emailed to say they were forbidden to wear the patch - a black and white Union flag with a "thin blue line" through it, the Sunday Express said.

The newspaper said officers had been keen to display the badge in the wake of the death of Pc David Phillips, who was knocked down by a stolen pick-up truck in Merseyside on Monday.

But senior officers are reportedly concerned that the badge could provoke ill-feeling or cause offence in some communities.

Ken Marsh, chairman of the Met Police Federation constables' branch, told the Sunday Express the email was sent around the time of Pc Phillips' death.

He said: "It told officers they couldn't wear it because it wasn't functional with regulations on police uniforms."

Mr Marsh added: "I don't see any way it can be deemed sensitive. Every officer in the British police force is British."

But earlier this week, after Pc Phillips' death, Met Commissioner Sir Bernard Hogan-Howe said he had "no issue" with his officers wearing the badge, the newspaper said.

Scotland Yard said the thin blue line badge could be worn with a supervisor's discretion, while officers can wear approved pins, badges and wristbands - the Police Memorial Day Badge, the Royal British Legion's Remembrance Day poppy and the Help For Heroes badge or wristband.

A Met spokesman said: "The Metropolitan Police Service has a dress code policy to clarify the dress standard expected from all staff, whether they are wearing uniform or plain clothes."